A Dual SIM mobile phone is one which holds two SIM cards. Initially, dual-SIM adapters were made available to use in regular mobile phones to allow them to contain two SIMs, and to switch from one to the other as required. This combination is called a standby dual-SIM phone. The first Dual SIM mobile phone was Benefon Twin manufactured by Benefon in Finland. It was launched on the market in 2000.
More recently, some phones have been produced that can natively work with two SIMs, both of which may be active at the same time. These are active dual-SIM phones. There are also some Chinese triple-SIM phones. Akai Trio is the first phone with triple GSM SIM slots
Dual-SIM operation allows the use of two services without the need to carry two phones at the same time. For example, the same handset can be used for business and private use with separate numbers and bills; or for travel, with an additional SIM for the country visited. Using multiple SIM cards allows the user to take advantage of different pricing plans for calls and text messages to certain destinations as well as mobile data usage.
These phones have until recent years been largely eschewed by the larger phone manufacturers partly due to their close ties with mobile phone networks who would prefer that customers use only one network exclusively. However more recently manufacturers such as Nokia and Samsung have started producing these phones, which will target customers mostly from developing countries
«Pseudo-Dual» - for convenience to use second SIM (as rule, it has «no major» slot for this) without both SIMs connected with owner's mobile service providers (MSP).
«Dual Sim Shift»
«Dual Sim Stand-by» (DSS) - allows the device to switch from one network to the other when required
«Dual Sim Active» (DSA) - allows the device to be connected to both networks at the same time (it's using transceiver). You can switch between the calls without dropping one (select Samsung models)
«Dual talk» - possibility to talk with 2 callers from different MSPs at same time
Active Dual SIM phones
Mobile phones with built-in simultaneous dual SIM capability allow both SIMs to be active simultaneously and allow calls to be received on either number at any given time. Most such phones have two transceivers built in one of which may support 2G and 3G while another may only support 2G.
Though a new generation of Dual SIM Phones, called "Dual SIM Dual Standby" (DSDS) provide the ability to have 2 active SIM simultaneously, using only one transceiver. This is for example technology used in Freeyourmobile M180 Dual SIM Mobile Phone, K-Touch A982, LG-GX200, Philips Xenium - X100, Samsung B7722, Samsung B5722 and Samsung E2152.
Battery life (talk time and standby time) of active dual-SIM mobile phones is reduced, typically by about a third. For instance, Device manufacturer Samsung declares a standby time for its Champ Duos E2652 Dual SIM phone of 476 hours when used with one SIM card and of 322 hours when used with two SIM cards. To compensate the shorter battery life, some Dual SIM phones ship with better capacity batteries, or in the case of Chinese-made phones, bundle their units with two batteries.
In November 2007, Verzio — a Singapore-based 3C (computing, communications, consumer electronics) brand launched the world's first 3G Dual-Triband dual-SIM model named Duplii. The same brand also launched the Twinn, 2.75G dual-SIM model. Powered by 2 processors, the Duplii and Twinn provide real dual-SIM real dual-connecting capability.
There are some little-known Chinese companies supplying inexpensive dual-SIM mobiles, mainly in Asian countries. The latest models includes W006 WiFi Dual Sim Mobile Phone, The M60 - Quadband Dual SIM Touchscreen mobile phone was launched in April 2010 being the 1st of the Chinese touch screen only mobiles with no keypad, including many features WiFi, Dual IMEI, Media playback & camera etc. to rival normal mobile phones.
Philips has made models Xenium 9@9w and 699 with this capability belonging to the restart to change active-line generation. Samsung also released the D880 DuoS in November 2007, a slider which can hold two SIM cards with simultaneous standby and the D780 which came much later both have limited function on the 2nd sim card, and there is a Windows Mobile based dual-sim phone too, called E-TEN glofiish DX900 (released in November 2008, been renamed to Acer Tempo DX900 in January 2009, after Acer bought E-TEN).
Popular Indian mobile companies such as Karbonn Mobiles, Micromax Mobile, Spice, Lemon Mobiles, LAVA Mobiles launch many feature phones with Dual SIM technology. Even few smart phones from these companies are Dual SIM based.
Reference : wikipedia.org
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